Camouflage textile materials used by hunters and by the military typically provide camouflage in the visible region of the electromagnetic radiation spectrum (400-700 nm). Due to the vastly diverse environments throughout the world, many different camouflage materials exist, including both visibly camouflaged and non-visibly camouflaged materials. The variety of environments (e.g., ranging from woodland to desert) necessitates the use of a variety of colors and patterns to create these camouflage textile materials. For instance, in a military woodland camouflage, the materials often use four colors: black, coyote, khaki, and green. In a military desert camouflage, the textile materials often use four colors: highland, light coyote, urban tan, and light tan. Many visible shade variations exist even within these two examples. Textiles with visible camouflage patterns are typically manufactured by printing the camouflage pattern on an undyed (greige) textile (e.g., woven, knit, non-woven, etc.) surface or by solution dying yarns that are subsequently woven or knitted into a camouflage pattern using, for instance, a jacquard process.
In some applications it is desirable to use textile materials that provide camouflage in other areas of the electromagnetic spectrum (e.g., beyond visible). In particular, advances in image intensifiers used in night vision equipment have heightened the need for improved camouflage in the near infrared (“nIR”) (i.e., 700-900 nm) and short wave infrared (SWIR) (i.e., 900-1700 nm) electromagnetic radiation spectrum. Typical night vision equipment amplifies low intensity electromagnetic radiation in the visible, nIR, and SWIR spectra, with specific sensitivity in the nIR and SWIR. Like camouflage in the visible spectrum, camouflage in the nIR and SWIR spectra enables the material, and thus the wearer or covered structure, to blend in with the environment. A primary difference is that, unlike the visible camouflage, nIR and SWIR camouflage does not involve a further segmentation of discrete bands of the spectrum (that in the visible gives rise to color separation). As such, effective camouflage in the nIR and SWIR spectra requires a material to have an appropriate balance of reflection, or reflectance, and transmittance/absorbance over the whole nIR and SWIR spectra. In addition, the ability to detect and identify an object using image intensifiers (such as night vision goggles) also depends on the ability to disrupt the silhouette or the shape of the object.
Conventional means for achieving desirable camouflage in both the visible, nIR, and SWIR is through a printing process wherein undyed textiles or textiles dyed to a base shade are printed to simultaneously achieve multiple colors (visible spectrum) and levels of nIR and SWIR reflectance. Most commonly, carbon black is added to the camouflage print ink or paste in varying amounts to vary the nIR and SWIR reflectance of the resulting textile. A disadvantage to this technique is that the carbon can negatively impact the desired visible shade of the camouflage textile and frequently results in a compromise between achieving appropriate visible and nIR camouflage, particularly in environments which require extremely light shades like the desert. In addition, topically treating textiles with such a carbon finish results in a textile material with poor nIR camouflage durability, as the topical carbon finishing can readily wash and/or wear off in use.
A further challenge in creating camouflage textiles which are suitable for the applications described is the need for comfort of the user. In outdoor environments, comfort in a variety of weather conditions requires that the textiles, and resulting articles, be liquidproof and breathable for optimum comfort. However, providing environmental protection by coating or lamination of liquidproof, breathable films or coatings can also affect the visible, nIR, and SWIR camouflage properties of the textile. For example, in the specific case of a liquidproof breathable film comprising microporous PTFE, the PTFE film often increases the overall reflectivity in the nIR spectrum, and possibly the visible spectrum as well, resulting in undesirable tradeoffs between durable environmental protection and nIR and SWIR camouflage.
Recent improvements to military camouflage have extended performance into the nIR portion and the short wave infrared (SWIR). Thus, there exists a need in the art for a camouflage material that achieves camouflage protection in both the nIR and SWIR spectra and that provides the desired physical and protection properties needed and comfort qualities desired in a camouflage garment.